A circuit breaker is used to protect an electrical circuit from damage caused by a persistent overcurrent condition or a very high current produced by a short circuit. During normal operation, a pair of contacts located within the circuit breaker are kept in a closed position to enable current flow through the circuit. When a fault condition is detected, the contacts are automatically opened, thus interrupting the circuit and disengaging the circuit from a power supply. When the fault condition is corrected, the contacts are again closed in order to resume normal operation.
An undesirable electric arc is formed when the circuit is interrupted. The arc jumps an air gap formed between the contacts which results in the continued flow of current. When the contacts open far enough the arc is extinguished and the current flow stops. The arc may cause erosion of the contacts, thus hindering further use of the circuit breaker. In addition, ionized gases may form inside the circuit breaker. If the arc is not extinguished quickly, pressure from the ionized gases could cause the circuit breaker to rupture.
An arc chamber may be used to quench the arc generated during separation of the contacts. The arc chamber includes several steel arc plates that surround the contacts. The arc plates serve to divide the arc into smaller arcs to thus promote the ultimate extinguishment of the arc.
The size of the air gap between the contacts is an important factor in determining the interrupting capacity of a circuit breaker. In particular, the interrupting capacity of the circuit breaker increases as the size of the air gap increases. However, increasing the size of the air gap in a conventional circuit breaker also requires an increase in the overall size of the circuit breaker itself. This is difficult to achieve since several applications for circuit breakers, such as circuit breakers used in the residential market, impose size constraints with respect to overall circuit breaker size. Therefore, an increase in the air gap is difficult to achieve in conventional circuit breakers due to limitations on package size, thus making it difficult to increase the interrupting capacity or to improve other performance characteristics of the circuit breaker.